Armature for electric speedometers



Jan. 30, 1940.

W. H. FARR ET AL ARMATURE FOR ELECTRIC SPEEDOMETERS Filed March 3, 1957 2 Sheets-Sheet 1 (82 ODOMETER llllm mar:

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?atented Jan. 30, 1940 UNITED STATES PATENT OFFICE ARMATURE FOR ELECTRIC SPEEDOMETERS I'Inia Application March 3, 1937, Serial No. 128,734

4 Claims.

The present invention relates to improvements in armatures for electric speedometers adapted for use with automotive vehicles, and is an improvement on the armature construction disclosed in application Serial No. 754,522, filed No- 1 vember 23, 1934.

In the electric speedometer forming the subject matter of the application referred to, there is disclosed an arrangement in which the speed indicator operating shaft is actuated by a pair of solenoids supplied with currents whose relative strengths depend upon the speed of the vehicle. The solenoids act on opposed armature members secured to the shaft in such manner that they impart rotation thereto in opposite directions. The opposed armature members are curved and tapered in such manner that the cross sectional area thereof decreases with the length. When current is supplied to the solenoids, the armatures are moved thereby until the force exerted by each solenoid on its associated armature is the same.

The force, of course, depends upon the cross sectional area of the armature and the current, so that for given values of current through the solenoids, the armatures are always actuated into predetermined positions.

By controlling the relative strengths of the currents supplied to the solenoids in response to variations in speed, the position of the armatures and, therefore, of the indicator shaft, is varied in accordance with the speed.

An object of the present invention is to provide an improved armature adapted to be used with electric speedometers.

Another object is to provide an improved unitary armature in which the movement of the armature by the solenoids, customarily used in electric speedometers, may be limited in both directions without the use of mechanical stops or the like.

Another object is to provide an improved armature having magnetic characteristics such that the movement of the armature is limited to a predetermined extent.

Further objects and advantages of the invention will appear from the ensuing description of a preferred embodiment and several modifications of the invention and in which reference will be had to the accompanying drawings in which:

Fig. 1 is a diagrammatic representation of the various mechanical elements of the speedometer and the manner in which they are connected in the electrical circuit of which they form a part;

Fig. 2 is a top plan view, partly in section, of the speed indicating unit and its actuating means;

Fig. 3 is a longitudinal vertical cross section taken on the line 3-3 of Fig. 2;

Fig. 4 is a top plan view of the improved armature construction of the present invention;

Fig. 5 is a partial cross sectional view of a modified armature construction, and

Fig. 6 is a partial cross sectional view of another modification.

Referring first to Fig. 1 of the drawings, there is shown an electrically operated speed indicating system forming no part of the present invention, but disclosed and claimed in the copending application of Horace M. Norman, Serial No. 127,845, filed February 26, 1937.

The system comprises a speed indicating arm Ill adapted to be moved by an electromagnetically operated actuating means l2, the position of which is controlled by a magnetically operated current varying means I4 suitably driven from a gear l6 rotating in unison with a'part,

such as a rear wheel, of a vehicle.

The various elements of the apparatus are indicated as being connected in circuitwith the ignition system of an automobile. Energy is supplied to the apparatus from the usual automobile battery l8 under the control of an ignition switch 20, shown in its open position, to which one terminal of the battery is connected by a conductor 22. The other terminal of the battery is grounded to the frame as indicated at The ignition switch 20 is connected by a conductor 26 to one end of a ballast resistance 28, the other end of which has connected thereto a pair of branch conductors 30 and 32, the former of which leads to the electromagnetically operated actuating means l2 and the latter to the magnetically operated current varying means I4.

The ballast resistance 28 is made of any suitable material having a high positive temperature coeflicient of resistance. Thus when the battery voltage is low the initial current flowing through the resistance is low and the resistance is relatively cooland permits a predetermined value of current to flow through the indicating apparatus. However, when the battery voltage is high, the initial current flow is relatively high and the resistance of the ballast resistance increases, thereby tending to maintain the current flow constant at said predetermined value.

The actuating means l2 comprises the unitary crescent-shaped armature 34, forming the subject matter of the present invention, having oppositely extending tapered portions 36 and 88 actuated by electromagnetic means, such as solenoids 40 and 42.

The armature 34 is mounted upon a supporting structure 44, in turn mounted upon a shaft 46. The latter actuates the indicator arm through gearing 48 and a shaft 60 upon which the indicator arm I0 is secured.

Solenoids 40 and 42 are connected in series with each other by a conductor 54 and have interposed in series therewith resistors 56 and 58, respectively. Resistors 56 and 58have negative temperature coefficients of resistance and resistance values proportioned to compensate for changes in the resistance of solenoids 40 and 42 caused by changes in temperature of the solenoids resulting from variations in current flow therethrough.

The circuit, including the solenoids and compensating resistors in series, is connected by the previously mentioned branch conductor 80 to the ballast resistance and by a conductor 60 to ground.

The branch conductor 82 is connected to one end of a fixed resistance 62, the other end of which is connected to ground through conductor 64 and the previously mentioned conductor 60. It is seen, therefore, that conductors 82 and 64 connect the resistance 62 in parallel with the series circuit including the solenoids 40 and 42 and the compensating resistors 56 and 58.

Associated with resistance 62 is a movable contact 66 connected by conductor 68 to conductor 64, and the position of which is controlled by the magnetically operated actuating means l4 in such manner that the position of the movable contact is dependent upon the rate of speed at which the vehicle is traveling.

The current varying means l4 may be constructed after the manner described in the copending application of Arden W. Le Fevre et al., Serial No. 40,600, filed September 14, 1935. It comprises a permanent magnet (not shown) rotated by shaft 10 suitably geared to the gear i6 and a cup-shaped rotor (also not shown) adapted to actuate the movable contact 66.

The rotor and contact 66 are both mounted on a shaft 12 biased by a spiral spring 14 to a predetermined position. The rotation of shaft 10 results in therotation of the permanent magnet and thereby of the shaft 12 against the bias of spring 14. The movable contact, therefore, assumes a position dependent upon the rate of rotation of the magnet and, therefore, also dependent upon the speed of the vehicle.

The electric speedometer also comprises a mileage indicator I6 which may be of the usual drum type. This indicator is driven through a spring biased pawl I8 actuated by an electromagnet 80. One terminal of the electromagnet is connected to the battery through conductor 82 and the ignition switch 20, and the other terminal thereof is connected by conductor 84 to a normally open cam actuated switch 86 adapted to be closed at predetermined distance intervals by a suitable mechanism driven by the previously described gear IS. The switch 86 is connected to ground through a conductor 88 and the previously mentioned conductor 60,

It is seen, therefore, that the magnet is connected in parallel with resistance 62 and the solenoids-40 and 42.

Before describing in detail the construction of the novel armature member forming the sub- Ject matter of the present invention, it may be well briefly to review the description of the operation of the above described electrical speedometer.

When the automobile is in motion the ignition switch 20 is normally closed, thereby establishing an electrical circuit through the three previously described parallel circuits, including the solenoids 40 and 42, the fixed resistance 62, and the magnet 80, respectively. The gear it rotates in unison with the vehicle wheels and drives the magnet shaft 10, which in turn rotates the magnet. The rotating field created by the magnet tends to rotate the shaft 12 and the movable contact 66 carried by the latter in the same direction as the magnet, and the strength of this tendency is directly proportional to the speed of rotation of the magnet. Thus the movable contact 66 assumes positions which at all times correspond to the speed of rotation of the magnet and, therefore, to the speed of the vehicle.

When the movable contact 66 is located centrally of theresistance 62, no current passes through the bridge circuit consisting of the movable contact and conductor 68, and consequently the same current passes through both solenoids 40 and 42 and resistors 66 and 58, which are in series with solenoids 40 and 42, respectively. Each of these solenoids attracts its associated portion of the armature with the same force, and the pointer l0 indicates a speed corresponding to approximately half the ultimate speed of the vehicle, or 44 miles an hour, as shown in the drawing.

When the speed of the vehicle is such that the movable contact 66 is moved toward one end of the resistance 62, a greater current passes through one of the solenoids than through the other. The solenoid receiving the strongest current exerts the greatest force upon its associated armature portion and draws a larger cross sectional part thereof into the solenoid, at the same time withdrawing the other armature portion from its associated solenoid. This movement of the armature portions and the pointer shaft continues until the shifting compensates for the difference in solenoid currents, whereupon the pointer shaft and pointer come to rest and indicate the speed of the vehicle, which corre-- sponds to the particular relationship of the solenoid currents then existing.

The negative temperature coefliclent resistors 56 and 58 maintain the resistance of the respective branch circuits in which they are placed constant at all times so that changes in temperature of the solenoids 40 and 42 are prevented from creating errors in the reading of the speedometer.

Referring now particularly to Figs. 2 and 3, the novel armature of the present invention is shown mounted in a speedometer actuating'unit, the constructional features of which form the subject matter of the copending application of Edward George Kelly, Serial No. 128,754, filed March 3, 1937. From these figures it may be seen that the armature 34 is secured by its support 44 for rotation with the vertically disposed shaft 46 journaled in bearings 90 and 92 adjustably mounted in an integral supporting structure '5 94. The latter comprises a substantially annular front support 96 and a rear support 98 connected by a pair of longitudinal vertically spaced apart upper and lower arms I00 and I02, respectively,

in which the bearings 90 and 92 are mounted.

The rear support 98 comprises three radially extending arms I04, I06 and. I08 provided with threaded openings whereby the rear support may be attached to a suitable part IIO of the vehicle by screw bolts H2.

The front support 96 is provided with a forward extending projection II4, upon which. is mounted a relatively narrow vertically extending web H6 and a cup-shaped member II8 secured to each other and the projection by bolts I20.

In the cup-shaped member is located a dial plate I22 suitable secured thereto and provided with suitable indicia with which the pointer I0 is associated.

The pointer I0 is secured to the end of the horizontally disposed shaft 50 mounted for rotation in the vertically extending web I I6 and a horizontally disposed V-shaped bracket I24. The latter is formed integral with the front support and extends substantially midway between the upper and lower arms I00 and I02 to near the center of these arms.

Movement is transmitted from the vertical shaft 46 to the horizontally disposed shaft 50 through a sector-shaped bevel gear I26 secured to the armature support 44 and a circular bevel gear I28 mounted on shaft 50 near the innermost end of the horizontal V-shaped bracket I24.

To return the pointer I0 and the shafts 46 and 50 to their zero positions, there is provided a spiral spring I30 having one end secured to the shaft 50 and the other to a fixed flange I32 projecting forward from a plate I34 adjustably mounted on web I I6 by screw bolts I36. From Fig. 3 it may be seen that the spring is secured to the shaft 50 between the dial plate I22 and the web II6. To prevent road shock or other vibrational forces from unduly affecting the pointer I0, there is provided an inertia wheel I38 frictionally mounted on a hub I40 secured to shaft adjacent the web.

The armature supporting means 44 comprises a horizontal portion I42 extending substantially parallel to the plane of the armature 34 and a vertical portion I44 extending substantially parallel to shaft 46. The horizontal portion I42 is secured to a hub I46 mounted on shaft 46 and has the sector gear I26 secured to the upper side thereof. A counterbalancing weight I48 is secured to the forward end of the horizontally disposed member I42, and is provided with a relatively heavy screw bolt I50, whereby further adjustment of the balance may be obtained.

The armature 34 is secured substantially centrally of its ends to a horizontal flange I52 formed at the end of the vertical portion I44 by a pair of bolts I54. Movement of the armature by either solenoid 40 or 42 is restricted by a central portion having a greater magnetic reluctance than the adjacent portions of the armature. The increased magnetic reluctance may be obtained by a number of different means, but in the construction shown in Fig. 3 it is obtained by positioning a relatively narrow non-magnetic filler strip I56 at the central portion of the armature.

From this figure it may be seen that the filler strip is placed between upper and lower lami-' nations I58 and I60, respectively. The laminated armature structure illustrated not only provides -a simple arrangement for constructing the armature, but also provides an armature having decreased hysteresis losses.

The solenoids 40 and 42 are adjustably secured to the upper horizontal arm I00 by integral metallic strips comprising bent end portions I62 and I63 substantially surrounding the lateral sides of the solenoids and fiat substantially hemispherical portions I64 and I66 secured to the horizontal arm I00. The semi-circular portions I64 and I66 are provided with an opening encircling a vertical boss I68 formed integrally with the horizontal arm I00 and are adapted to be rotated thereabout by an adjusting wheel I10 provided with a toothed portion I12 adapted to engage coinciding toothed portions I14 provided on the semi-circular portions.

This arrangement provides means whereby the two solenoids may be rotated simultaneously in order to secure proper adjustment thereof with respect to the tapered portions 36 and 38 of the armature. During the initial assembly operation, and before the wheel I10 has been installed, the solenoids may be individually adjusted to the desired positions. At any time subsequent to complete assembly of the instrument the solenoids may be individually adjusted if desider by simply removing the adjusting wheel I10 and adjusting the solenoids by hand. However, after the instrument has been once assembled such individual adjustment is ordinarily unnecessary.

The tapered portions of the armature extend through central openings I14 in each solenoid. The solenoids are suitably insulated from the tapered portions of the armature, as well as from the encircling supports I62 by insulating material I16.'

The actuating unit described above is also provided with means for supporting a part of the electrical system shown in Fig. 1. For this purpose there is provided a cup-shaped insulating member I80 secured to the rear support 98 by a plurality of screw bolts I82. The resistors 56 and 58 are secured to the insulating cupshaped member by bolts I84 (only one of which is shown), which also are adapted to act as terminals. The ballast resistance 28 is secured between one of the terminals I84 and a third terminal I86.

In Fig. 4 there is illustrated the exact shape of the armature 34. From this figure it may be seen that the oppositely extending armature portions 36 and 38 have cross sectional areas that decrease progressively with their length and that the armature when considered as a whole has a shape substantially that of a crescent. The tapered portions 36 and 38 are uniformly tapered, that is, if their cross sectional area is plotted against angularity, the resulting curve is a straight line.

The laminations of which the armature is constructed are secured together by a plurality of rivets I81 suitably spaced along the length of the armature. The laminations are also secured further by the bolts I54 by means of which the armature is mounted to the horizontally disposed flange I52 of the armature supporting means 44. The bolts I54 not only serve to hold 9 together the laminations, but also serve to hold the non-magnetic filler strip I56 securely in place.

In the modified form of armature construction illustrated in Fig. 5, the outer layers I58 and I of the laminations are constructed as in the modification shown in Fig. 4, but the intermediate laminations I88 are cut away in part in order to provide an air space I90. It is obvious that the increased magnetic reluc- -tance in this modification is provided by the decreased cross sectional area of the central portion.

In the further modified form oi construction illustrated in Fig. 6, the armature is constructed from a solid piece of metal I92 and has a slot or groove I94 cut in its central portion, whereby the magnetic reluctance thereof is increased by decreasing the cross sectional area of the armature.

In operation the solenoids are supplied with currents whose values are varied in response to the speed of the vehicle, and as a result of the current variation the armature portions 38 and 38 are actuated to move the pointer ill to indicate the speed of the vehicle, as described above.

Utilization of armatures of the type described above eliminates the requirement of mechanical stops, for the reason that when the portion oi the armature having the greatest cross section area is drawn into the field of the solenoid, that portion remains there irrespective of the increased value of the current supplied to the solenoid.

It should be understood that the invention is not limited to the various modifications described above. but may assume other forms as well, and that the scope or the invention is limited solely by the following claims.

We claim:

1. An armature for use with electrical indicating apparatus of the type utilizing solenoids supplied with selectively varied currents for actuating said armature in opposite directions, in-

eluding in combination, a pair of oppositely extending armature portions having progressively decreasing cross sectional areas each adapted to be actuated by a respective one oi said solenoids, and a central portion having a cross sectional area substantially less than the adjacent portions of, said oppositely extending armature portions.

2. An armature comprising a pair of oppositely extending tapered armature portions having the ends of lesser magnetic reluctance joined by a portion of substantially greater magnetic reluctance.

3. A laminated armature comprising a plurality oi laminations of substantially crescent shape, some of said laminations having a part thereof cut away substantially centrally intermediate the ends of the crescent whereby the central portion of the armature has a magnetic reluctance greater than the armature portions immediately adjacent.

4. A laminated armature comprising a plurality of laminations of magnetic material having substantially a crescent shape, some of said laminations having a part thereof cut away substantially centrally intermediate the ends of the crescent, said cut away parts being replaced by a solid non-magnetic material forming a support for the laminations which are not cut away, whereby the armature is provided with an intermediate portion of greater magnetic reluctance than the armature portions immediately adjacent.

WIILARD H. FARR. GEORGE E. COXON. 

